Products derived from a printing machine are frequently folded into thirds when intended for production of books. A folding apparatus for such products is described in the referenced Lange German Patent 29 20 625, see especially FIG. 5 thereof. The web is cut between a cutter blade cylinder and a combination needling-folding blade cylinder to format length and subsequently transferred into a folding jaw of a folding jaw cylinder, during which transfer the sheet is folded in the relationship of 2/3 to .OMEGA.. Upon subsequent transfer into the folding jaw of a further folding jaw cylinder, a second cross fold to one-third of the length of the format is obtained.
This arrangement has the advantage that the needles are at the outer margins, so that a needling strip can be used in which the needle portion can be cut off with low loss of paper. This is important in the production of books. The operating speed of the folding arrangement, however, is limited by the fact that, upon forming the first cross fold, two-thirds of the sheet must be pulled off by the combination needling-folding blade cylinder counter its direction of rotation.
The referenced literature, "Braun, Atlas des Zeitungsund Illustrationsdruckes" ("Braun, Atlas of Newspaper and Magazine Printing"), published by Polygraph Verlag GmbH, Frankfurt am Main, 1960, p. 95, describes a folding apparatus in which, first, a web is cut to the required length of the format between a cutter blade cylinder and the combination needling and folding blade cylinder. The cut sheet can be folded to two-thirds of its length upon transfer into the folding jaws of a folding jaw cylinder, by suitably locating the operating elements thereof. The folded jaw is then transferred to grippers of a combination gripper-folding blade cylinder which, upon subsequent transfers into the folding jaw of a folding jaw cylinder, the sheet is folded to one-third of the length of the format.
The arrangement as described prevents pull-off of two-thirds of the length of a sheet counter the direction of rotation of a cylinder. On the other hand, the use of grippers also decreases the operating speed and the needling holes in the fold products are at the inside, so that the waste and loss of paper upon cutting and trimming is high.